Closing assemblies of this generic type are disclosed, for example, in EP 1 457 642 A2 and US 2002/0127105 A1. Both closing assemblies essentially comprise two side parts which are inserted into the remaining intermediate space between the first and the last blades of a blade ring. Since each side part is in each case hooked to a projection, which forms the undercut, on the circumferential groove and both side parts can therefore be moved into the intermediate space, the two side parts together are narrower, when seen in the axial direction, than the intermediate space to be filled and to be closed. After the two side parts have been fitted, a space once again remains free between them, and must be filled with an intermediate part. The intermediate part secures the two side parts against axial movement releasing the respective hook and therefore against falling out of the circumferential groove. In order to secure the intermediate part itself against falling out, it is equipped with in each case two lip-like webs, each of which is bent by plastic deformation into a pocket which is provided on each side part. In consequence, the intermediate part with each side part is hooked in an interlocking manner, as a consequence of which the two side parts are likewise held in the circumferential groove. US 2002/0127105A1 also proposes that the intermediate part be hooked via a dovetail to the first and the last blade of the blade ring, while in contrast, according to EP 1 457 642 A1, each side part of the closing assembly is hooked to the first and the last blade of the blade ring. This essentially prevents gap formation and enlargement between adjacent rotor blades and the closing assembly in the circumferential direction.
However, the known closing assemblies have the disadvantage that, in order to remove the closing assembly, it must be at least partially destroyed in the area of the interlock, which is costly. It should also be noted that the closing assembly must withstand the thermal and mechanical loads which occur, in particular the centrifugal force which occurs during operation, when it is mounted in the rotor of turbomachinery.
Furthermore, Patent Specification 809 689 from the German Patent Office discloses a closing assembly having two side parts which can move with respect to one another and between which a trapezoidal clamping element is provided in order to brace the two parts in a circumferential groove in a rotor. Once the parts of the closing assembly have been inserted into the circumferential groove, the trapezoidal clamping element can be raised in the direction of the groove opening by means of a screw which is supported on the groove base of the circumferential groove. This results in the two side parts being moved apart from one another, so that their shoulders engage behind the projections on the circumferential groove.
In this case, it has been found to be disadvantageous that the screw which is required to raise the clamping element is supported on the groove base of the circumferential groove. As a result of the different thermal expansions of the rotor and the components of the closing assembly, and because of the effects of centrifugal force, the contact of the screw and groove base can accidentally become undone, as a result of which the closing assembly is no longer seated securely.
In addition, blade root locking with two halves is known from Laid-Open Specification DE 29 34 298. The two halves can each be hooked to the projections which are arranged on the side walls of the circumferential groove. In order to secure the two halves in the groove at a distance, and therefore hooked, they are in the form of split threaded nuts so that one securing screw can be screwed in between them.
Furthermore, U.S. Pat. No. 2,421,855 discloses a turbine blade lock which hooks the two parts of the closing assembly to the undercuts in the circumferential groove, by raising a trapezoidal clamping element.
Furthermore, GB 1 270 540 and DE 26 15 701 disclose deformable attachment means which can be used to connect two parts to one another.